provider/google: update DNS names in tests.

[paddycarver]

Our DNS tests were using terraform.test as a DNS name, which GCP was
erroring on, as we haven't proven we own the domain (and can't, as we
don't). To solve this, I updated the tests to use hashicorptest.com,
which we do own, and which we have proven ownership of. The tests now
pass.

Test output after changes:

=== RUN   TestAccDnsManagedZone_basic
--- PASS: TestAccDnsManagedZone_basic (3.51s)
=== RUN   TestAccDnsRecordSet_basic
--- PASS: TestAccDnsRecordSet_basic (25.45s)
=== RUN   TestAccDnsRecordSet_modify
--- PASS: TestAccDnsRecordSet_modify (159.13s)
=== RUN   TestAccDnsRecordSet_changeType
--- PASS: TestAccDnsRecordSet_changeType (36.80s)
PASS

Test output before changes:

=== RUN TestAccDnsRecordSet_basic
 --- FAIL: TestAccDnsRecordSet_basic (0.41s) testing.go:265: Step 0 error: Error applying: 1 error(s) occurred: * google_dns_managed_zone.parent-zone: Error creating DNS ManagedZone: googleapi: Error 400: Please verify ownership of the 'terraform.test.' domain (or a parent) at http://www.google.com/webmasters/verification/ and try again, verifyManagedZoneDnsNameOwnership FAIL

[stack72]

LGTM!

[ghost]

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